According to a widespread design, the boxing machines include a magazine, in which the tubular blanks are piled up, in flat folded configuration, and then withdrawn therefrom one by one, erected to define open boxes, and finally placed onto a box conveying line, which extends besides an article conveying line; the box conveying line and the article conveying line are moved in reciprocal step relation. The articles are introduced into the boxes by pushing means, moving longitudinally, synchronously with said conveying lines, and operated crosswise thereto; the boxes are then closed by suitable devices, situated downstream, along the box conveying line.
Erecting flat folded tubular blanks into boxes, after their withdrawal from the magazine, is known in technical jargon as “rhombus-opening”, and includes the rotation of the box sides, along articulation lines (creasing) already made in the blank, so as to set them at right angles with respect to the two remaining horizontal sides.
Many technical solutions have been invented to carry out the above mentioned operation, each of which aimed at optimizing the results in relation to two factors: the first factor is the blanks natural tendency to close again, due to the elastic return, as a reaction to the erecting action, and the second factor is the need to make the machine suitable for box different sizes.
The above technical. solutions are divided, due to the design basic idea, into two types: the first type includes erecting of the blanks by the striking against stop elements and the other one includes means, which are controlled to act positively on the blanks.
Moreover, there are known hybrid solutions, including both controlled erecting means and fixed stop elements.
When the action of the controlled means is aimed at making the box edge-resting sides rotate in the same direction as the machine feeding direction, an opening action occurs which is known as “positive opening”.
A solution of known type, conceived by the owner of this Application, includes withdrawing the flat folded blank from the bottom of the magazine, bringing the same to strike first fixed stop elements, which cause its erecting, and consequently erecting the box. Then, the box is placed on an additional conveying line, having second fixed stop elements, aimed at keeping erected the box, which is subsequently brought to the proper box conveying line, prepared for receiving the articles in the above mentioned way.
The drawbacks of this technical solution result from a certain difficulty in setting the position of various fixed stop elements, to minimize the blank elastic return, when it is placed on the additional conveying line.
Actually, during this passage, the blank is already disengaged from the first stop elements, but not yet engaged with the second ones.
The above setting up difficulties are further remarked at every size changeover, due to different dimensions and/or different proper characteristics of the elastic return of each type of box.
The obvious consequences of the above mentioned drawback are the machine prolonged downtimes at size changeover, the necessity of tests and adjustment fine tuning, as well as the increase of the jamming possibility, in particular during the passage between the additional conveying line and the box conveying line, if the boxes are not correctly squared.